First, I am so sorry your little guy is not feeling well. Sounds like the daycare was leaving dogs unattended and it is likely he was able to get into something he shouldn't have.
At this point, I think you have to trust your vet. Sounds like something was found in a fecal exam and he is being given immediate attention. I would certainly trust the vet's diagnosis over "guessing" from the internet.
I hope he is feeling better and back home soon. Please keep us updated.